RPE question

Trying to understand something. On STrength III template week 9, If I am “supposed” to squat 405 for 1 at rpe 8, but my warmup at 315 feels like rpe 10, should I drop wight from 315 and do what I think is 1x4 at rpe 9, and then drop more and do the 3x4sets at 80%?

Yes, precisely.